The present invention relates to apparatus and methods for adjusting the NO.sub.x level of emissions of heavy-duty gas turbines for emissions compliance without disassembly of the combustors and particularly relates to a mechanical arrangement enabling external access to the dilution air sleeves for the combustion chamber for adjusting the combustor dilution air flow hole areas and methods of adjustment.
Heavy-duty gas turbines employing dry low NO.sub.x combustion systems are typically installed with predetermined dilution flow hole areas for flowing compressor discharge air into the combustion liner to shape the gas temperature profile exiting the combustion system and provide reduced NO.sub.x emissions. Dilution air flow sleeves are typically provided and have a predetermined hole area for flowing compressor discharge air into the combustion liner. Not infrequently, however, and after installation of the turbine at the power generation site, the NO.sub.x emissions level is either too high or too low, with corresponding CO emissions level that is too high. This is a result of the normal variability of machine air flow fraction that is delivered to the combustor and the resulting variability of flame temperature in the NO.sub.x producing zones of the combustor.
Under those circumstances, the turbine is typically brought into NO.sub.x emissions compliance by removal of the combustion liners from the turbine and resizing the dilution holes to redistribute the combustor air flow. This procedure requires the physical removal of the combustion liner from the turbine with attendant removal of certain piping for fuel, as well as piping for oil and water systems and auxiliary air piping for atomization. It is also necessary to remove the heavy end cover of the combustor to gain access to the dilution holes. Further, there is the possibility of contaminating the fuel system in the process of removing and reassembling the various piping systems. Still further, this process can take between one to two weeks' time, during which there is a gas turbine outage, preventing the electricity provider from producing power during that period of time. Consequently, there is a need for a system which facilitates change of the combustor dilution hole areas without disassembly and subsequent reassembly of major portions of the combustor and in a reduced timeframe.